1. Field of the Invention
The present invention relates to a stripline mount for semiconductor lasers and, more particularly, to a stripline mount for high frequency applications which is capable of compensating the impedance of a semiconductor laser to provide improved impedance control between the laser and a high frequency modulation current source.
2. Description of the Prior Art
Semiconductor laser devices are used in a wide variety of applications due to their compactness, relatively high efficiency, and well-controlled output. However, a number of requirements are imposed upon these semiconductor laser devices. For durability, cooling of the laser element is necessary, since prolonged high temperature operation of such a laser can seriously damage and even destroy the device. Further, since the output light intensity from a laser is a function of the junction temperature of the device, the supporting structure of the laser must be able to absorb the tremendous amount of heat generated by a laser in its operating state. There exist many arrangements in the prior art for solving these problems, related to the inclusion of a thermo-electric cooler (TEC) as part of the mounting structure of the laser. U.S. Pat. No. 4,338,577 discloses one such exemplary arrangement. While it is relatively simple to solve these temperature related problems, other problems develop when the laser is operated at extremely high bit rates, for example, in the range of 500 Mb/s and above. At these speeds, the low impedance of the laser relative to that of the signal source and the parasitics associated with the interconnecting network become critical factors. Minimizing these parasitics and matching the impedance of the interconnecting network to the laser impedance over a broad bandwidth must be performed in order to achieve acceptable performance. It is well known that semiconductor lasers exhibit an impedance in the range of 5-8 ohms, while most high frequency modulation current sources, used in typical high bit rate laser transmitters, have a very high output impedance. Without control, this mismatch would cause a strongly frequency dependent coupling from the input signal source to the laser. Severe waveform distortion would result from multiple signal reflections. Additionally, since every laser will exhibit a slightly different impedance, an empirical solution to this problem is inadequate. Therefore, a need remains in the prior art for an arrangement which allows a laser diode to be connected to a high frequency input signal, and preferably, allows the laser to be coupled uniformly to the signal source over a wide bandwith.